In various medical procedures, a needle or cannula is introduced into the body, either for the purpose of removing tissue or delivering a substance to the tissue. An example of the former situation is fine needle aspiration needle biopsy (FNAB) in which a needle is inserted into an organ (e.g., the liver, lung, brain, thyroid) and cells are removed for the purpose of diagnosing a condition, such as cancer. An example of the latter is convection-enhanced delivery (CED) in which drugs are continuously infused into the brain tissue using a cannula.
Whether the needle or cannula is used to remove tissue or deliver a substance to the tissue, it is desirable to prevent travel of the tissue or substance along the pathway formed by the needle or cannula. For instance, in cases in which cancer cells are being removed in a biopsy procedure, it is desirable to prevent the spread of such cells to other parts of the patient's tissue when the biopsy needle is withdrawn. In the case of drug delivery, it is desirable to prevent the drug from flowing backwards along the pathway formed by the delivery cannula. Unfortunately, it is difficult to ensure that such unintended results do not happen. For instance, drug backflow is common when high infusion rates are used.
In view of the above discussion, it can be appreciated that it would be desirable to have an apparatus and method for blocking needle and cannula tracts to prevent the migration of patient tissue and/or delivered substances within the body.